Double acting hydraulic pump

ABSTRACT

A double acting hydraulic pump and air motor therefor including means for controlling the inlet and exhaust of air to and from the opposite sides of the piston in the air cylinder. The pump has a stepped diameter housing including an upper pump cylinder defining an outlet chamber for liquid and a lower pump cylinder received within the upper pump cylinder and defining an inlet chamber for liquid. A pump piston reciprocates in the two cylinders and is slidably received in two axially spaced stationary packing sleeves having a resilient spacer sleeve interposed axially therebetween. The spacer sleeve is formed of metal sheet adapted to deflect resiliently under load. The upper end of the upper pump cylinder is received within a recess in the lower end of the air motor housing. A retainer plate connected to the lower end of the air motor housing is provided with an opening to allow passage of the upper end of the upper pump cylinder and a pair of radially extending ears thereon. The pump housing is rotatable about its own longitudinal axis to align or misalign the ears and the opening and retain the pump housing to or release it from the motor housing.

Unite States Patent [191 osen et a1.

[11] 3,827,339 Aug. 6, 1974 1 1 DOUBLE ACTING HYDRAULIC PUMP [73] Assignee: Nordson Corporation, Amherst,

Ohio

[22] Filed: May 17, 1971 [21] Appl. No.: 144,055

Related U.S. Application Data [63] Continuation-impart of Ser. No. 809,235, March 21,

[52] US. Cl 92/152, 92/169, 417/554 [51] Int. Cl. F011) 7/00 [58] Field of Search 92/181, 152, 52, 169; 417/545, 554

[56] References Cited UNITED STATES PATENTS 530,350 12/1894 Rosenkranz 417/554 623,357 4/1899 Evans 92/152 1,097,632 5/1914 l-lolmes..... 92/169 1,601,472 9/1926 Gates 417/554 1,785,834 12/1930 Kilgore 417/554 1.925,444 9/1933 Grieshaber.... 92/152 2,178,822 11/1939 Upton 417/554 2,835,005 5/1958 Green 92/169 3,302,535 2/1967 Procter et al. 92/52 3,543,682 12/1970 Farrow 417/554 FOREIGN PATENTS OR APPLICATIONS 169,018 9/1921 Great Britain 417/554 Primary Examiner-Charles J. Myhre Assistant Examiner-R. l-i. Lazarus Attorney, Agent, or Firm--Bosworth, Sessions & McCoy 57 ABSTRACT A double acting hydraulic pump and air motor therefor including means for controlling the inlet and exhaust of air to and from the opposite sides of the piston in the air cylinder. The pump has a stepped diameter housing including an upper pump cylinder defining an outlet chamber for liquid and a lower pump cylinder received within the upper pump cylinder and defining an inlet chamber for liquid. A pump piston reciprocates in the two cylinders and is slidably received in two axially spaced stationary packing sleeves having a resilient spacer sleeve interposed axially therebetween. The spacer sleeve is formed of metal sheet adapted to deflect resiliently under load. The upper end of the upper pump cylinder is received within a recess in the lower end of the air motor housing. A retainer plate connected to the lower end of the air motor housing is provided with an opening to allow passage of the upper end of the upper pump cylinder and a pair of radially extending ears thereon. The pump housing is rotatable about its own longitudinal axis to align or misalign the ears and the opening and retain the pump housing to or release it from the motor housing.

2 Claims, 6 Drawing Figures minnows 61814 3.827. 339

INVENTORS SAMUEL R. ROSEN,

' flo ALVIN A. R000 8.

DONALD R. SCHARF ATTORNEYS INVENTORS.

L R. ROSEN W 9L W ATTORNEYS swam, 339 v SAMUE ALVIN A. ROOD 8 DONALD R. SCHARF SHEEY 2 OF 3 PAIENIEBAUB elm CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-impart of applicants copending application Ser. No. 809,235, filed Mar. 21, 1969.

BACKGROUND OF THE INVENTION This invention relates to pneumatic motors and double acting improved and especially to such a pump having an im proved construction. One aspect of the invention relates to the manner in which the pump is retained to the air motor.

The invention has particular utility in connection with double acting liquid pumps used to pump liquid paint to a spray gun.

In many applications it is desirable to employ a pump having a stepped diameter housing, that is, a housing having a portion of greater diameter to permit holding packings having a substantial wall thickness through which the pump piston slides and having another portion of smaller diameter to obtain minimal clearance volume for the piston. Such minimal clearance volume is desirable to facilitate priming and positive charging on the intake stroke. The stepped diameter housings have, in the past, been made as one piece and when rebuilt require special tools to remove the packings.

Another problem in the art to which our invention relates is that of providing appropriate spacing means between axially spaced packing sleeves through which the pump piston slides in reciprocating within the pump cylinder. The friction of the piston in sliding through such packings may generate an axial force thereon tending to displace them. It is desirable to maintain the packings in their proper position without any such shift. Ordinary fixed length spacers between the packings are generally used but are somewhat unsuitable because the accumulation of tolerances on the lengths of the parts precludes a precise fit of the spacer. A fixed spacer may thus be used to reduce the clearances between the packings but not to eliminate such clearances. In some applications a spring may be effective to eliminate the clearance but in most cases the space available for the spacer is not readily adaptable to use of a coiled spring and, in addition, such springs usually require a high preload to render them sufficiently rigid.

Still another problem in the art to which our invention relates is that of making the pump and driving air motor easily and conveniently connectable and disconnectable for maintenance and repair.

As indicated above, the invention has particular utility in connection with pumps used in conjunction with air motors for pumping paint or hot paint in the socalled hot airless method of spray painting. This method is disclosed and discussed in detail in US. Pat. Nos. 2,754,228 and 2,763,575 of James A. Bede. In this method the paint, whether hot or cold, is projected from a small orifice nozzle under high pressure and the continuity of an even pressure is most desirable to obtain the best results.

SUMMARY OF THE INVENTION A general object of this invention is to provide a hydraulic pump that overcomes the disadvantages noted above in prior pumps of the type described.

A particular object is to provide a hydraulic pump having a stepped diameter housing that is constructed in two pieces to facilitate machining of the pieces and to eliminate the need for tools to remove packings when the pump is rebuilt.

Another object of the invention is to provide a resilient spacer sleeve for use between two axially spaced packings in a pump cylinder that is sufficiently resilient to eliminate clearances between the spacer sleeve and the packing sleeves while being sufficiently rigid to prevent excessive deflection of the packings as the pump piston reciprocates therein.

Another object of the invention is to provide a hydraulic pump and a pneumatic motor for driving the pump in which the pump and driving air motor are easily connected and disconnected to facilitate maintenance and repair of each.

Finally, it is an object of this invention to provide a single piston double acting hydraulic pump that is efficient, easily maintained, easily repaired and rugged in construction and economical to make and maintain.

These and other objects and advantages are accomplished by the provision of a hydraulic pump having a piston reciprocable within a cylindrical housing of stepped diameter. The housing includes an upper pump cylinder, closure means defining a sealing path for the piston at the lower end of the upper pump cylinder, and a lower pump cylinder of lesser diameter than the upper pump cylinder received within the upper cylin der in sealing engagement with the closure means. Means are provided for retaining the lower cylinder within the upper cylinder in sealing engagement therewith. The pump piston passes between the upper and lower cylinders in sealing contact with the closure means.

According to another aspect of the invention there is provided, between two axially spaced packing sleeves through which the pump piston passes, a spacer sleeve of metal sheet that is resiliently deflectible under load.

According to still another aspect of the invention the hydraulic pump is combined with an air motor having a housing and a piston adapted to be drivingly connected to the piston of the pump. The motor housing has a recess in the lower end thereof to receive the upper end of the pump housing which has outwardly extending projections at its upper end. A retainer plate is connected to the bottom of the motor housing and has an opening therein to allow passage of the upper end of the pump housing and the outwardly extending projections thereon. The pump housing is rotatable about its own longitudinal axis to align the projections with the opening in the retainer plate to allow passage of the projections and is also rotatable to misalign the projections and the opening to retain the pump housing connected to the motor housing. In this manner the air motor and hydraulic pump may be easily connected and disconnected for maintenance and repair of either.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front elevation of a double acting liquid pump and associated single cylinder, double acting air motor embodying the invention;

FIG. 2 is a side elevation of the pump and air motor of FIG. 1;

FIG. 3 is a broken cross-sectional view of the pump of FIGS. 1 and 2, drawn to an enlarged scale and taken on the line 33 of FIG. ll;

FIG. 4 is a fragmentary sectional view taken on the line 4-4 of FIG. 3;

FIG. 5 is a cross-sectional view taken on the line 5-5 of FIG. 3; and

FIG. 6 is a cross-sectional view taken on the line 66 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to the drawings and initially to FIGS. 1 and 2 there is shown a paint spraying apparatus for use in spraying liquid paint according to the so-called airless method described above in the Background of the Invention. The apparatus comprises a double acting hydraulic pump A, driven by a double acting air motor B, and adapted to pump paint from a paint pail C to a spray gun D.

Paint from the paint pail C which may be, for example, a standardsize drum, enters the hydraulic pump A through an inlet fitting 10 located at the bottom thereof and exits through an outlet fitting 11. From the outlet fitting 11 the paint is directed to another fitting 12 on a paint filter 13 mounted on the pump A. The paint filter 13 serves to filter out solid particles within the paint that may be too large to pass through the nozzle of the spray gun D.

The paint from the filter 13 exits through an outlet fitting 14 to a flexible hose 15 which extends to the spray gun D. The hose 15 is of sufficient length and is made of flexible material so that it will provide some dampening effect in case of variable pressure output from the double acting pump A. The hose 15 being resilient and flexible, absorbs some energy at the peak pressure periods and thus gives a smoother more uniform pressure output to the spray gun D. The hydraulic pump A cycles at a rate typically about 40 cycles per minute and in a typical instance would have about a 4 cubic inch displacement.

Located at the upper end of the pump A is a solvent chamber 16 and an associated filler cup 17. The chamber 16 maintains a bath of paint solvent around the upper end of the pump piston 18 to dissolve any paint which may accumulate thereon and which when dry could seriously damage the packing through which the upper end of the pump piston 18 slides during its pumping travel.

Air pressure for operating the air motor B is supplied by an air pump (not shown) through a pressure line 21 which is connected to a pressure regulator valve 22 secured to the air motor B. Air is exhausted from the air motor B through a muffler 23 which serves to attenuate the noise of the escaping air. A pressure gauge 24 is located at the top of the air motor B (FIG. 2).

The double acting air motor B shown somewhat diagrammatically in FIG. 2 comprises an air cylinder 30 mounted between an upper cylinder head 31 and a lower cylinder head 32. The heads 31 and 32 are preferably formed of cast aluminum while the air cylinder 30 is of aluminum tube stock which has its interior surface hard anodized to accomodate frictional loads and to minimize wear. Within the cylinder 30 is a piston 33 mounted on a tubular piston rod 34.

Operating air enters the cylinder chamber and is exhausted therefrom in opposite phase through inletexhaust passages 35 and 36 located in the upper cylinder head 31 and lower cylinder head 32 respectively. The control of the inlet and exhaust of air from the respective ends of the cylinder chamber is accomplished by upper and lower poppet type operating valves 37 and 38 respectively.

The valves 37 and 38 are located in an operating valve housing or block 40 bolted at one end to the upper cylinder head 31 and at the other end to the lower cylinder head 32. The block40 has a central air supply passage 41 extending therethrough, which receives operating air from the pressure regulator valve 22 through an inlet fitting 42. Each of the valves 37 and 38 is pilot operated, and has a control head 43 and an operating head 44.

The valves control the inlet and exhaust of air to the cylinder through inlet-exhaust passages 52 and 53 respectively formed in the valve block 40 and which communicate with the inletexhaust passages 35 and 36 respectively in the upper cylinder head 31 and lower cylinder head 32.

The position of the operating valve 37 is controlled by a pilot valve while the position of the operating valve 38 is controlled by a pilot relay valve (not shown). The pilot and pilot relay valves are housed in a pilot valve block 65 which is bolted to the top face of the upper cylinder head 31 with suitable seals interposed therebetween.

The control system for the pneumatic motor including the poppet valves 37, 38 and the pilot and pilot relay valves is more fully described and is claimed in applicants copending application identified above. a

The construction of the pump A is best illustrated in FIGS. 3 through 6 and it includes the solvent chamber 16 as well as the pumping cylinder itself. The solvent chamber 16 is formed in part by the lower cylinder head 32 of the air motor B and by a matching solvent chamber block 120. The block and the lower cylinder head 32 have a sliding fit with one another and are held in axial position by flange bolts or tie rods 121 which extend up to the upper cylinder head 31 and serve to secure the air cylinder assembly and block 120 together.

A solvent enters the solvent chamber 16 through the filler cup 17 and is most advantageously maintained near the top of the filler. The solvent serves to dissolve any paint which may collect on the surface of the piston 18 and which could dry thereon and by abrasive action seriously damage the packings through which the piston 18 slides.

The pumping action is accomplished within a cylindrical housing including an upper pump cylinder 122 and lower pump cylinder 123. The upper end of the upper pump cylinder 122 is secured to the solvent chamber block 120 in a circular recess 127 in the bottom thereof by a retainer plate 124. The upper pump cylinder 122 has a pair of radially extending ears 125 adjacent its upper end and the retainer plate 124 has a central opening 126 contoured to receive the upper end of the upper pump cylinder 122 and the ears 125 when in one condition. However, the upper pump cylinder 122 when inserted is rotated 90 so that the ears are retained by the retainer plate 124 in the recess 127 (FIG. 4). This manner of retaining the pump housing to the air motor allows for very easy assembly and disassembly for maintainance and repair.

Located within the upper pump cylinder 122 is an upper packing sleeve 128 which seals and guides the piston 18 by means of a packing assembly 129 carried therein. Another packing sleeve 131) is mounted in the lower end of the upper pump cylinder 122, the sleeve 138 also having a packing assembly 131.

The spacing between the packing sleeves 128 and 130 must be accurately fixed and the packing sleeves prevented from excessive movement axially as the piston 18 reciprocates. A solid spacer sleeve would therefore require extremely accurate dimensioning and would not accommodate dimensional variations in other parts such as the packing sleeves themselves.

The pump of the present invention however has a resilient expanded metal spacer sleeve 132 which maintains proper spacing between the packing sleeves 128 and 130 while at the same time being resilient enough to accommodate some dimensional variations in other parts. The sleeve 132 is formed of expanded metal which after being expanded according to practices well known in the art is rolled into a flat sheet form. The sleeve may also be formed of sheet metal that is perforated in a regular pattern to render it axially deflectible. The rolled sheet is then cut to size and formed into a cylinder which may or may not have its lateral surface abutted. Accordingly, the spacer sleeve 132 can be compressed while still exerting sufficient force to maintain the packing sleeves 128 and 130 in spaced apart relation and prevent axial movement thereof as the piston 18 slides therethrough. While a round wire coil spring could serve the same purpose, it would require excessive space to provide the same force and rate and thus would be undesirable.

The lower pump cylinder 123 fits within the upper pump cylinder 122 in the manner shown in FIG. 3 with its upper end resting against the bottom of the lower packing sleeve 130. The lower pump cylinder is retained within the upper pump cylinder as shown in FIGS. 3 and 6. A flange 133 on the lower pump cylinder 123 rests upon a ledge 133a on the inner walls of upper cylinder 122. Lower pump cylinder 123 is provided with a pair of projections 123a, 123b below flange 133 which align with correspondingly shaped openings 122a and 122b in ledge 133a. The lower pump cylinder is inserted downwardly into the upper pump cylinder with the projections 123a, 123b in registry with the openings 122a, 1221; until the flange 133 of the lower pump cylinder comes to rest upon ledge 133a and the lower pump cylinder is supported thereby. The lower pump cylinder then will not rotate while attaching fittings and or hose to intake of the pump.

Several advantages result from the two piece con struction of the pump housing. No special tools are required to remove the packings when the pump is rebuilt. Removal of packings can be accomplished merely by telescoping the lower pump cylinder 123 within the upper pump cylinder 122. Also, the two smaller pieces of the pump housing facilitate machining operations during making of the housing and, because a lower number of critical dimensions occur on each of the upper and lower cylinders, the rejection rate of pieces can be lowered.

The piston 18 has an upper end 134 of smaller diameter which travels entirely within the upper pump cylinder 122 and the solvent chamber 16, and also a tubular lower end 135 of enlarged diameter with an axial passage 136 located therein. The upper end 134 of the piston is connected to the lower end of the piston rod 34 of the air cylinder at a threaded connection indicated at 137 in FIG. 2. A

The upper pump cylinder 122 and lower pump cylinder 123 define an outlet chamber 138 and an inlet chamber 139 respectively, the passage 136 within the lower end 135 of the piston 18 being in communication with the outlet chamber 138 through ports 140 at the upper. end thereof. A ball check 141 is located at the inlet fitting 10 to the pump inlet chamber 139 and a second ball check 1412 is located in the passage 136 at the lower end 135 of the piston 18.

Considering reciprocating movement of the piston 18 beginning with the piston extended downwardly to the lower end of the pump housing, the beginning of the upward retraction movement will open the ball check 141 and close the ball check 142. and liquid paint will be drawn into the pump inlet chamber 139. This continues until the piston 18 reaches its retracted or raised position shown in FIG. 3.

During the same upward retraction movement, liquid paint located in the pump outlet chamber 138 will be forced out through the outlet fitting 11. The volume pumped out through the outlet fitting 11 during this movement is one-half the volume drawn into the inlet chamber 139.

During the downward extension movement of thepiston 18 the ball check 141 will close and the ball check 142 will open so that paint in the pump inlet chamber 139 will be forced through the axial passage 136 in the lower end 135 of the piston 18 and into the outlet chamber 138.

Since essentially all of the liquid paint in the inlet chamber 139 will be displaced during the downward extension movement and since only one-half the volume of the inlet chamber 139 is displaced out the port, the other half remaining in the chamber 138, one-half of the volume paint which is pumped out of the inlet chamber 139 will also be pumped out of the outlet chamber 138 through the outlet fitting 11.

Accordingly an equal volume of paint is pumped during both extension and retraction movement of the piston 18 so that a generally uniform output of liquid paint is supplied to the spray gun D, the only interruption in pressure output occurring at the instant that the piston 18 reverses its travel.

The transient variation in output occurring at the instant of piston travel reversal however, is dampened out in the supply hose 15 from the filter 13 to the spray gun D, which is generally 25 feet or longer to provide a dampening effect due to the resilient character of the hose.

While the invention has been shown anddescribed with reference to a specific embodiment thereof this is for the purpose of illustration rather than limitation and other modifications and variations will be apparent to those skilled in the art upon reading of the specification, all with the intended spirit and scope of the invention. Accordingly the patent is not to be limited to the form specifically illustrated and described not in any manner that is inconsistent with the extent to which the progress in the art has been advanced by the invention.

What is claimed is:

l. A hydraulic pump comprising an upper pump cylinder defining an outlet chamber for liquid, a ledge on said cylinder projecting radially into said outlet chamber at the lower end thereof, a lower pump cylinder defining an inlet chamber for liquid of lesser diameter than said outlet chamber, said lower cylinder having a radially outwardly extending flange seated on said ledge to connect said lower cylinder to said upper cylinder, a pair of axially spaced packing sleeves sealing the upper and lower ends of said outlet chamber, the lower of said packing sleeves being seated on said flange in sealing engagement therewith and closing the in slidable sealing contact with said lower packing sleeve to pump liquid into said inlet chamber and out of said outlet chamber.

2. A pump as claimed in claim 1 wherein said spacing means includes a resilient spacer sleeve in said outlet chamber interposed axially between said packing sleeves, said spacer sleeve being formed of metal sheet adapted to deflect resiliently under load.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2 ,339 Dated August 1974 Inventor) Samuel R. Ro'sen, Alvin H. Rood and Donald R. Scharf It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, delete the first sentence of the "Background of the Invention" and insert therefore-This invention relates to pneumatic motors and double acting liquid pumps, andespecially to such a pump having an improved -con st.ruction.--

Signed and sealed this 8th day of October 1974.

(SEAL) Attest: I

McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents ORH ra-losox'lo-es) p USCOMM-DC eC376-PQB I V us sown-up" rumn acrnu nu a-nl-an 

1. A hydraulic pump comprising an upper pump cylinder defining an outlet chamber for liquid, a ledge on said cylinder projecting radially into said outlet chamber at the lower end thereof, a lower pump cylinder defining an inlet chamber for liquid of lesser diameter than said outlet chamber, said lower cylinder having a radially outwardly extending flange seated on said ledge to connect said lower cylinder to said upper cylinder, a pair of axially spaced packing sleeves sealing the upper and lower ends of said outlet chamber, the lower of said packing sleeves being seated on said flange in sealing engagement therewith and closing the lower end of said outlet chamber, means holding said packing sleeves in spaced relation, and a piston of slightly smaller diameter than said inlet chamber and substantially smaller diameter than said outlet chamber reciprocable within said upper and lower cylinders and adapted to pass from one to the other of said chambers in slidable sealing contact with said lower packing sleeve to pump liquid into said inlet chamber and out of said outlet chamber.
 2. A pump as claimed in claim 1 wherein said spacing means includes a resilient spacer sleeve in said outlet chamber interposed axially between said packing sleeves, said spacer sleeve being formed of metal sheet adapted to deflect resiliently under load. 